1. Technical Field
The present disclosure relates to reminder circuits, and particularly to a energy-saving reminder circuit to remind users to shut off a standby voltage after a computer is powered off.
2. Description of Related Art
In a personal computer (PC) system, power management is adopted to conserve energy. While the PC is powered, it can be put in a sleep mode to save energy when not in use. System power states derived from the advanced configuration and power interface (ACPI) specification are defined as follows:
S0/Working—The central processing unit (CPU) is fully up and operating; devices are powering up and down as needed.
S1—The CPU is stopped; the random access memory (RAM) is refreshed; the system is operating in a low power mode.
S2—The CPU has no power; the RAM is refreshed; the system is in a lower power mode than S1.
S3—The CPU has no power; the RAM is in slow refresh; the power supply is generally in a reduced power mode (for example, the power supply not supplying much power and is operating in a lower power efficiency mode).
S4—The hardware is completely off; the system memory has been saved to disk.
S5/Off—the hardware is completely off; the operating system has shut down; nothing has been saved.
When the computer is powered off and in the S5/off state, there is still a +5 volt standby voltage (+5VSB) applied to the motherboard for driving a basic power source control circuit of the computer system during the off state. However, this means the computer still consumes energy in the off state, which is a waste of energy.